MT: single key can be used as both modifier key and normal key. It works as modifier key when keep hold the key, and it works as normal key when just tapped the key. SandS is a kind of MT, abbr of Space and Shift. It works as its name suggests.

LT; single key can be used as both temporary switching layer key and normal key, similar to MT.

Why is it important is because I want to place useful functions on most accessible keys.